Downhole operations, including well production or completion, particularly for oil and natural gas wells, utilize various drill string members that must maintain high wear resistance and fracture toughness while also meeting other design requirements.
It is a long-standing practice in the design and manufacture of such downhole tools and components to apply wear-resistant hardfacing materials to surfaces that are subject to abrasive wear during downhole operations. In the past, these hardfacing compositions generally comprised various carbides of the elements of Groups IVB, VB, and VIB in a matrix metal of iron, cobalt, or nickel and alloys and mixtures thereof. Hardfacing materials have generally been applied by melting the matrix of the hardfacing material and a portion of the surface to which the hardfacing is applied using various methods. The various carbide particles give the hardfacing material hardness and wear resistance, while the matrix metal lends the hardfacing material fracture toughness. A hardfacing material must generally strike an adequate balance between wear resistance, which is generally associated with its hardness, and fracture toughness.
Many factors affect the suitability of a hardfacing composition for a particular application. These factors have generally included the chemical composition and physical structure of the carbides employed in the composition, the chemical composition and microstructure of the matrix metal or alloy, and the relative proportions of the carbide materials to one another and to the matrix metal or alloy. However, as the complexity of downhole operations and associated instrumentation increases, other factors also have bearing on the suitability of a hardfacing composition for a particular application. One such factor is the magnetic properties, such as the magnetic permeability, of the hardfacing material. Hardfacing materials have generally not been designed to control the magnetic permeability, and generally have had high magnetic permeability. However, the increased complexity and sensitivity of downhole instrumentation to extraneous magnetic fields, or to alteration of the magnetic fields produced by the instrumentation, associated with the hardfacing materials used to protection them makes it very desirable to identify hardfacing materials that have controlled magnetic properties, particularly reduced magnetic permeability, so as to avoid interference with magnetic measurements in the region of the instrumentation.
Therefore, it is desirable to provide downhole tools and components that provide high wear resistance and fracture toughness, as well as a reduced magnetic permeability.